Observed time difference of arrival (otdoa) positioning in wireless communication networks

ABSTRACT

Aspects of the disclosure provide a method for observed time difference of arrival (OTDOA) positioning. The method can include receiving from a serving cell of a first network assistance data for measuring time difference of arrival of positioning reference signals (PRSs) received from a plurality of neighboring cells of a second network, receiving from the serving cell a gap pattern for decoding a master information block (MIB) of a first neighboring cell of the plurality of neighboring cells, or a system frame number (SFN) offset of the first neighboring cell, and determining an SFN timing of the first neighboring cell based on the gap pattern for decoding the MIB of the first neighboring cell or the SFN offset of the first neighboring cell.

BACKGROUND

Wireless communication networks can employ various positioningtechniques to determine a position of user equipment. For example,Observed Time Difference of Arrival (OTDOA) positioning is a downlinkpositioning technique specified in Long Term Evolution (LTE) standardsdeveloped by the 3rd Generation Partnership Project (3GPP). OTDOApositioning relies on a target device measuring a difference in the timeof arrival of Positioning Reference Signals (PRSs) that the targetdevice receives from neighboring base stations.

SUMMARY

According to one aspect of the present disclosure, there is provided afirst method for Observed Time Difference of Arrival (OTDOA)positioning. The first method can include receiving from a serving cellof a first network assistance data for measuring a time difference ofarrival of Positioning Reference Signals (PRSs) that can be receivedfrom a plurality of neighboring cells of a second network. The firstmethod can further include receiving from the serving cell a gap patternfor decoding a Master Information Block (MIB) of a first neighboringcell of the plurality of neighboring cells, or a System Frame Number(SFN) offset of the first neighboring cell, and determining an SFNtiming of the first neighboring cell based on the gap pattern fordecoding the MIB of the first neighboring cell or the SFN offset of thefirst neighboring cell. In one example, the assistance data includes atleast one of cell identity information of the plurality of neighboringcells, PRS configuration information of the plurality of neighboringcells, and SFN timing information of the plurality of neighboring cellseach indicating an offset between a neighboring cell or a reference cellthat is one of the plurality of neighboring cells.

Optionally, embodiments of the first method can further includetransmitting a decoding request for a measurement gap for decoding theMIB of the first neighboring cell, the decoding request including anidentity of the first neighboring cell without specifying a timing ofthe measurement gap. The gap pattern can include a measurement gap thatmatches a MIB transmission of the first neighboring cell. Optionally andalternatively, in any of the preceding aspects, the gap pattern caninclude a measurement gap having a time length longer than a MIBtransmission period of the first neighboring cell.

Optionally, in any of the preceding aspects, the first method canfurther include determining timings of PRS positioning occasions of oneor more of the plurality of neighboring cells based on the SFN timing ofthe first neighboring cell and the assistance data, and transmitting ameasurement request for a set of measurement gaps for measuring thePRSs, the measurement request including timings of the set ofmeasurement gaps that match the PRS positioning occasions of the one ormore of the plurality of neighboring cells. The first method can furtherinclude transmitting measurements of the time difference of arrival ofthe PRSs obtained by measuring the PRSs during the set of measurementgaps.

According to another aspect of the disclosure, there is provided asecond method for OTDOA positioning that can include transmitting by aserving cell of a first network to a User Equipment (UE) assistance datafor measuring time difference of arrival of PRSs received from aplurality of neighboring cells of a second network at the UE, andtransmitting by the serving cell a first gap pattern for decoding a MIBof a first neighboring cell of the plurality of neighboring cells, or anSFN offset of the first neighboring cell, in order to determine an SFNtiming of the first neighboring cell at the UE.

Optionally, embodiments of the second method can further includereceiving by the serving cell a decoding request for a measurement gapfor decoding the MIB of the first neighboring cell, the decoding requestincluding an identity of the first neighboring cell without specifying atiming of the measurement gap. Optionally, in any of the precedingaspects, the first gap pattern includes a measurement gap that matches aMIB transmission of the first neighboring cell. Optionally andalternatively, in any of the preceding aspects, the first gap patternincludes a measurement gap having a time length longer than a MIBtransmission period of the first neighboring cell.

Optionally, in any of the preceding aspects, the second method canfurther include receiving by the serving cell a measurement request fora set of measurement gaps for measuring the PRSs, the measurementrequest including timings of the set of measurement gaps that match PRSpositioning occasions of one or more of the plurality of neighboringcells, transmitting by the serving cell a second gap pattern includingthe requested set of measurement gaps in response to receiving themeasurement request for the set of measurement gaps, and receiving bythe serving cell measurements of the time difference of arrival of thePRSs from the UE. The SFN offset of the first neighboring cell isdefined according to a modulus; for example, the SFN offset of the firstneighboring cell may be defined modulo 1024.

According to a further aspect of the present disclosure, there isprovided a UE for OTDOA positioning. The UE can include a memory storagecomprising instructions, and one or more processor in communication withthe memory. The one or more processors can execute the instructions toreceive from a serving cell of a first network assistance data formeasuring time difference of arrival of PRSs received from a pluralityof neighboring cells of a second network, receive from the serving cella gap pattern for decoding a MIB of a first neighboring cell of theplurality of neighboring cells, or an SFN offset of the firstneighboring cell, and determine an SFN timing of the first neighboringcell based on the gap pattern for decoding the MIB of the firstneighboring cell or the SFN offset of the first neighboring cell.

Optionally, in an embodiment of the UE, the one or more processor canexecute the instructions to transmit a decoding request for ameasurement gap for decoding the MIB of the first neighboring cell, thedecoding request including an identity of the first neighboring cellwithout specifying a timing of the measurement gap. The gap pattern caninclude a measurement gap that matches a MIB transmission of the firstneighboring cell. Optionally and alternatively, in any of the precedingaspects the gap pattern can include a measurement gap having a timelength longer than a MIB transmission period of the first neighboringcell.

Optionally, in any of the preceding aspects, the one or more processorcan execute the instructions to determine timings of PRS positioningoccasions of one or more of the plurality of neighboring cells based onthe SFN timing of the first neighboring cell and the assistance data,and transmit a measurement request for a set of measurement gaps formeasuring the PRSs, the measurement request including timings of the setof measurement gaps that match the PRS positioning occasions of the oneor more of the plurality of neighboring cells. In any of the precedingaspects, the one or more processor can execute the instructions totransmit measurements of the time difference of arrival of the PRSsobtained by measuring the PRSs during the set of measurement gaps. Thefirst network can be an NR network, and the second network can be an LTEnetwork.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of this disclosure that are proposed as exampleswill be described in detail with reference to the following figures,wherein like numerals reference like elements, and wherein:

FIG. 1 shows an exemplary communication network that includes a LongTerm Evolution (LTE) network and a New Radio (NR) network;

FIG. 2 shows an exemplary Positioning Reference Signal (PRS)configuration according to an embodiment of the disclosure;

FIG. 3 shows an example Reference Signal Time Difference (RSTD)measurement process according to an embodiment of the disclosure;

FIG. 4 shows a flowchart of an exemplary Observed Time Difference ofArrival (OTDOA) positioning process according to an embodiment of thedisclosure;

FIG. 5 shows a flowchart of another exemplary OTDOA positioning processaccording to an embodiment of the disclosure;

FIG. 6 shows an exemplary block diagram of user equipment (UE) accordingto an embodiment of the disclosure; and

FIG. 7 shows an exemplary block diagram of a base station according toan embodiment of the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Aspects of this disclosure describe a system and method for ObservedTime Difference of Arrival (OTDOA) positioning in wireless communicationnetworks. More specifically, the disclosure describes techniques forobtaining a System Frame Number (SFN) of a neighboring cell during anOTDOA positioning process to determine a position of a target device.The neighboring cell can be associated with a first wireless networkthat is configured to support OTDOA positioning, while the target devicecan be associated with a second wireless network that does not supportOTDOA positioning.

During the OTDOA positioning process, a location server can provide thetarget device with positioning assistance data via the second wirelessnetwork. The positioning assistance data can include identification ofone or more neighboring cells that belong to the first wireless networkand are adjacent to the target device. Further, the assistance data caninclude positioning reference signal (PRS) timings of each of theneighboring cells that are defined with respect to an SFN timing of therespective neighboring cell, while SFN timings of each neighboring cellcan be specified with respect to a reference cell that is a member ofthe listed neighboring cells. Based on the techniques described herein,an SFN timing of one of the listed neighboring cells can be obtained,and accordingly the timings of the PRSs can be determined. Determiningthe SFN timing of the reference cell may comprise first determining theSFN timing of a neighboring cell different from the reference cell,followed by inferring, from the SFN timing of the neighboring cell, theSFN timing of the reference cell based on the assistance data.

FIG. 1 shows an exemplary communication network 100 that includes a LongTerm Evolution (LTE) network 101 and a New Radio (NR) network 102. TheLTE network 101 and the NR network 102 coexist in the communicationnetwork 100. In one example, the LTE network 101 can include an LTE corenetwork 120 and a plurality of eNodeB base stations, such as eNodeB basestations 131-133, that are connected to the LTE core network 120. The NRnetwork 102 can include an NR core network 150 and a plurality of gNBbase stations, such as the gNB base station 160. In addition, thecommunication network 100 includes a location server 110 that can beconnected to the LTE core network 120 and the NR core network 150.

According to this exemplary embodiment, the LTE network 101 can be anetwork compliant with 3rd Generation Partnership Project (3GPP) LTEstandards, while the NR network 102 can be a network compliant with 3GPPNR standards. While the LTE network 101 and the NR network 102 are usedas examples in FIG. 1, the present disclosure is not limited to a LTEnetwork and a NR network. The techniques described herein can also beapplicable to other types of wireless communication networks that maycompliant to other communication standards and coexist with each other.

The location server 110 can be deployed as part of either the LTE corenetwork 120 or the NR core network 150, or can be dependent from the LTEcore network 120 and the NR core network 150. However, the locationserver 110 can be associated to both of the LTE core network 120 and theNR core network 150. In one example, the location server 110 performsfunctions of an Evolved Serving Mobile Location Center (E-SMLC) asdefined in LTE standards, and is deployed in the LTE core network 120.In another example, the location server 110 performs location managementfunctions (LMF) as defined in NR standards as well as functions of anE-SMLC, and is deployed in the NR core network 150.

The eNodeB base stations 131-133 can be base stations implementing aneNodeB node specified in the 3GPP LTE standards, while the gNB basestation 160 can be a base station implementing a gNB node specified inthe 3GPP NR standards. Each base station 131-133 or 160 can transmitradio signals towards certain directions to cover a geographical areathat is referred to as a cell. A cell can be assigned a cell identity bywhich it can be identified in the wireless communication network 100. InFIG. 1, cells 141-143 are formed by the eNodeB base stations 131-133,respectively, while a cell 161 is formed by the gNB base station 160.Transmission or reception of signals from a base station can be said tobe transmission or reception of the signals from a cell associated withthe respective base station.

As shown in FIG. 1, the communication network can include user equipment(UE) 170. The UE 170 can be any device capable of wirelesslycommunicating with the communication network 100, such as a mobilephone, a laptop computer, a vehicle carried device, and the like. In theFIG. 1 example, the UE 170 is able to operate on the LTE network 101, aswell as the NR network 102. Accordingly, the UE 170 includes circuitsconfigured to perform signal processing in accordance with the LTEstandards and the NR standards. In one example, the NR network 102 andthe LTE network 101 are configured to operate on different frequencybands. For example, the gNB base station 160 operates on millimeter wavebands while eNodeB base stations 131-133 operate on frequency bands withlower frequencies. Accordingly, the UE 170 can include a transceiverconfigured to operate on respective different frequencies.

In the FIG. 1 example, the UE 170 is wirelessly connected to the gNBbase station 160. For example, the UE 170 can operate in a connectedmode maintaining a radio resource control (RRC) connection between theUE 170 and the gNB base station 160. Alternatively, the UE 170 canoperate in an idle mode but monitoring signals transmitted from the gNBbase station 160. As shown in FIG. 1, the UE 170 is under the coverageof the cells 141-143 and 161. As the UE 170 is connected to the gNB basestation 160 and ready to be served by the gNB 160, the cell 161 isreferred to as a serving cell of the UE 170, while the other cells141-143 are referred to as neighboring cells of the UE 170. Of course,there can be a plurality of neighboring cells that cover the UE 170, butare not shown in FIG. 1.

In one example, the OTDOA positioning, a downlink positioning scheme, isused to locate the UE 170. In OTDOA positioning, a target devicemeasures PRSs from a plurality of cells that may include a serving celland/or neighboring cells, and determines differences in time of arrivalof PRSs between a reference cell and other cells. For example, theserving cell can be used as the reference cell which provides a timebaseline for determining the differences in time of arrival of PRSs.This process is referred to as a Reference Signal Time Difference (RSTD)measurement process. The difference between a pair of cells candetermine a hyperbola, and intersections of at least two hyperbolae candetermine a position of the target device. Positions of base stations ofthe measured cells can be used for the determination.

In the FIG. 1 example, the LTE network 101 is configured to support theOTDOA positioning, while the NR network 102 does not support the OTDOApositioning. To facilitate the RSTD measurement, the eNodeB basestations 131-133 of the LTE network 101 are configured to transmit PRSsperiodically. Transmission of PRSs, referred to as positioningoccasions, can be based on a PRS configuration. The PRS configurationspecifies when PRS positioning occasions will take place with respect toan SFN of a respective base station transmitting the respective PRSs.

In addition, to facilitate the RSTD measurement, the location server 110can be configured to provide assistance data to the UE 170, receive RSTDmeasurements from the UE 170, and accordingly calculate a location ofthe UE 170. Specifically, in one example, the location server 110 cancommunicate with the eNodeB base stations 131-133, for example, usingLTE Positioning Protocol A (LPPa) specified in 3GPP standards. Byexchanging of LPPa messages, the location server 110 can collectinformation from the eNodeB base stations 131-133. For example, thecollected information can include PRS configurations, SFN timinginformation, frame timing information, cell identifications, antennacoordinates corresponding to neighboring cells 141-143. The locationserver 110 can further generate assistance data based on the collecteddata (or information from other sources), and provide the assistancedata to the UE 170. In one example, the assistance data is transmittedto the UE 170 using LTE Positioning Protocol (LPP) specified in 3GPPstandards. The assistance data can include the PRS configurations, theSFN timing information, the frame timing information, and the cellidentities of the neighboring cells 141-143.

Assuming the UE 170 is connected to the eNodeB base station 131, basedon the assistance data, the UE 170 can typically determine timings ofPRS positioning occasions of the neighboring cells 141-143, andaccordingly capture the PRS transmission during the PRS positioningoccasions to perform RSTD measurement. For example, in the assistancedata, the serving cell 141 can be used as a reference cell, and SFNtimings and frame timings of other neighboring cells 142-143 can bespecified with respect to this reference cell 141. A frame timing canrefer to one of time points when frames are sequentially transmitted. AnSFN timing can refer to one of time points when frames having certainSFNs are transmitted. As an example, a frame timing offset of aneighboring cell with respect to the reference cell 141 can be providedin the assistance data, and the corresponding SFN timing information canbe provided in a form of an SFN offset with respect to the SFN of thereference cell 141. In an alternative example, frame boundaries of theserving cell 141 and the neighboring cells 142-14 can be synchronized,meaning frame timing offset equals zero. Accordingly, the assistancedata may not include frame timing offset information, but includes SFNoffset information.

As the UE 170 is assumed to be connected to the eNodeB base station 131,the UE 170 knows SFN timings of its serving cell 141 (frame timings ofthe serving cell 141 and SFNs of each frame received from the servingcell). Accordingly, the UE 170 may be able to determine frame timingsand SFN timings of the neighboring cells 142-143 based on the assistancedata.

As described above, in the FIG. 1 example the UE 170 is connected to theNR network 102 that does not support the OTDOA positioning, andtherefore the above described OTDOA positioning cannot be readilyperformed to locate the UE 170. Specifically, the gNB base station 160may not transmit PRSs due to configuration. In addition, the locationserver 110 cannot collect information about the serving cell 161 of theUE 170, and consequently does not include the serving cell 161 as one ofthe cells listed in assistance data for OTDOA measurement. However, theassistance data can still be transmitted to the UE 170 through the NRcore network 150 and the gNB base station 160, for example, by using theLPP messages. The transmission of the assistance data can be transparentfor the gNB base station 160. For example, the assistance data may betransmitted as signaling of a Non-Access Stratum (NAS) protocol. One ofthe neighboring cells 141-143 can be used as a reference cell in theassistance data, instead of a serving cell.

According to an aspect of the disclosure, under the above circumstanceswhere the UE 170 is connected to a serving cell that is not included inpositioning assistance data, the UE 170 can obtain an SFN timing of atleast one of the neighboring cells included in the assistance data. Theat least one of the neighboring cells can be a reference cell asspecified in the assistance data, or can be a neighboring cell otherthan the reference cell. In one example, the UE 170 can read a MIB of aneighboring cell to obtain the SFN information. For example, the UE 170can send a request to the serving cell 161 for a measurement gap, andcan decode a MIB of one of the neighboring cells listed in theassistance data during the measurement gap. In another example, the gNB160 can provide an SFN offset and a frame timing offset of a neighboringcell listed in the assistance data to the UE 170 as a response to arequest from the UE 170. As a result, a location of the UE 170 beingconnected to a network that does not support the OTDOA positioning canbe determined.

In various examples, the SFN timing of a neighboring cell can berepresented as a combination of a frame timing offset with respect tothe serving cell 161 (or in other words, a frame timing differencebetween the neighboring cell and the serving cell 161) and an SFN of theneighboring cell. Accordingly, obtaining an SFN timing of theneighboring cell is equivalent to obtaining a frame timing offset and anSFN of the neighboring cell. While in FIG. 1 example three neighboringcells 141-143 are listed as neighboring cells in the assistance data,number of neighboring cells listed in assistance data can be more thanthree, for example, 10, 20 or more than 20 in other examples.

FIG. 2 shows an exemplary PRS configuration 200 according to anembodiment of the disclosure. A sequence of sub-frames 201 starting at afirst sub-frame of a frame with SFN=0 is shown in FIG. 2. PRSpositioning occasions 210 a -210 c take place periodically among thesequence of sub-frames 201. The PRS configuration 200 in the time domaincan be defined by three parameters. A first parameter 210 is PRSpositioning occasion that refers to a number of consecutive sub-framesthat carry PRSs. For example, each of the PRS positioning occasions 210a, 210 b, or 210 c can include 1, 2, 4, or 6 sub-frames. A secondparameter 220 is PRS transmission period 220. For example, a PRStransmission period can last for 160, 320, 640, or 1280 sub-frames. Athird parameter is PRS sub-frame offset that refers to a number ofsub-frames before the first PRS positioning occasion 210 a since thebeginning of the first frame with SFN=0. As shown, when SFN timings ofthe sequence of sub-frames are known, PRS positioning occasion timingscan be determined based on the PRS configuration.

FIG. 3 shows an example RSTD measurement process 300 according to anembodiment of the disclosure. During the process 300, an SFN of aneighboring cell is obtained by reading a MIB of the neighboring cell.In the FIG. 3 example, the UE 170 is connected to the NR serving cell161, and the LTE neighboring cell 141 is used as a reference cell in theassistance data provided by the location server 110. The process 300 canbe performed to obtain an SFN of the neighboring cell 141 as well asframe timings of the neighboring cell 141.

Three time lines 310-330 corresponding to the LTE neighboring cell 141,the NR serving cell 161, and the UE 170, respectively, are shown in FIG.3. The first timeline 310 includes a sequence of sub-frames 301-306carrying MIBs. Each of the sub-frames 301-306 can be a first sub-frameof one of a sequence of consecutive frames transmitted from theneighboring cell 141. Thus, the MIBs have a transmission period of oneframe. Each MIB can carry SFN information, and decoding a MIB can obtainan SFN of a respective frame that carries the MIB. Each sub-frame301-306 can also carry one or more synchronization sequences transmittedbefore the SFN information, such as primary synchronization signal (PSS)and secondary synchronization signal (SSS). The UE 170 can accordinglyobtain the frame timings of the neighboring cell 141 by reading thosesynchronization sequences. In addition, the first time line 310 alsoshows a sequence of PRS positioning occasions 311-312. PRSs of the PRSpositioning occasions 311-312 are transmitted from the neighboring cell141 according to a PRS configuration.

The second time line 320 includes multiple measurement gaps 321-323. Ameasurement gap refers to a time period configured for performing aninter-frequency measurement. For example, a UE is connected to a servingcell operating on a first carrier frequency, and performs a measurement(such as RSTD measurement) of signals received from a neighboring celloperating on a second carrier frequency. The UE can send a requestthrough an RRC connection to the serving cell for one or moremeasurement gaps. Optionally, in the request, timings and duration ofthe measurement gaps can be specified. As a response to the request, theserving cell can configure the measurement gaps for the UE and return ameasurement gap pattern. For example, a measurement gap pattern caninclude one or more measurement gaps that each has a starting time and atime length. During the measurement gaps, no uplink or downlink datatransmission is scheduled for the UE. The UE can switch from the servingcell frequency to the neighboring cell frequency to perform aninter-frequency measurement, and subsequently switch back to the servingcell. Duration of a measurement gap can include time for switchingbetween different carrier frequencies, and time for performing themeasurement.

In a first example, the serving cell 161 of the NR network 102 knowsframe timings of the neighboring cell 141 of the LTE network 101. Forexample, as part of a configuration of the NR network 102, frame timingsof the neighboring cell 141 are provided to the serving cell 161 in aform of frame timing offsets with respect to the serving cell 161.Accordingly, when requesting a measurement gap for reading a MIB of theneighboring cell 141, the UE 170 can specify a purpose of themeasurement gap (to read MIB) but without specifying a particular timeof the measurement gap. The serving cell 161 knows MIB timings (frametimings) of the neighboring cell 141, and can accordingly schedule ameasurement gap 321 that matches a transmission of a MIB, such as thesub-frame 302 in the FIG. 3 example. In one example, the measurement gap321 lasts for about 2 ms. In alternative examples, the measurement gap321 can take other lengths.

In a second example, the serving cell 161 does not have knowledge offrame timings of the neighboring cell 141. In this case, a longermeasurement gap 323 than the measurement gap 321 can be configured. Forexample, the measurement gap 323 can have duration suitable for the UE170 to decode a MIB of the neighboring cell 141 without knowing theframe timings. In one example, the measurement gap 323 has a time lengthlonger than a frame. For example, frames on time line 310 have durationof 10 ms, and the measurement gap 323 is configured to be about 11 ms orlonger than 11 ms. Under such configuration, at least one sub-framecarrying a MIB can be captured within the span of the measurement gap323. In alternative example, more than one measurement gap 321 or 323can be configured. For example, when the neighboring cell is of lowsignal quality, decoding MIBs may be tried more than once. The timing ofthe more than one measurement gap may facilitate receiver behaviors suchas combining of different transmission instances of the MIB, forinstance, allowing the receiver to overcome bad radio conditions.

The measurement gap 322 can be configured for RSTD measurement. Forexample, after SFN and frame timing of the neighboring cell 141 areobtained, based on assistance data from the location server 110, the UE170 can determine timings of PRS positioning occasions of theneighboring cells 141-143. Accordingly, the UE 170 can send a second gaprequest to the serving cell 161 specifying a gap pattern including oneor more measurement gaps matching the PRS positioning occasions of theneighboring cells 141-143.

In one example, the neighboring cells 141-143 operate on a samefrequency, and frame timings of the neighboring cells 141-143 aresynchronized. In addition, PRS configurations of the neighboring cells141-143 are configured in a way that the PRS positioning occasions ofthe neighboring cells 141-143 are aligned in time (transmitted during asame sub-frame). In this case, one measurement gap 322 can be used toperform the RSTD measurement towards PRSs from the three neighboringcells 141-143. In one example, a time length of the measurement gap 322can be determined based on duration of the to-be-measured PRSpositioning occasions in addition to time used for switching betweendifferent carrier frequencies.

In another example, PRS positioning occasions of the neighboring cells141-143 can take place at different times, for example, due to PRSconfigurations or asynchronization among the neighboring cells 141-143.Or, the neighboring cells 141-143 can operate on different carrierfrequencies which may require RSTD measurement be performed separatelyon different carrier frequencies. Accordingly, multiple measure gaps canbe configured for the RSTD measurement.

As shown, the process 300 includes multiple steps 341-344. At step 341,the UE 170 sends a first gap request (also referred to as a decodingrequest) for a first measurement gap in order to decode a MIB of theneighboring cell 141. The first gap request may not include a timing ofthe measurement gap. As a response to the first gap request, themeasurement gap 321 or 323 can be configured by the serving cell 161depending on whether the serving cell 161 knows the frame timings of theneighboring cell 141. At step 342, the UE 170 decodes a MIB carried onthe sub-frame 302 during the measurement gap 321, or decodes a MIBcarried on a sub-frame within the measurement gap 323, to obtain theSFN. At the same time, based on synchronization sequences carried on asub-frame, frame timings of the neighboring cell 141 can be obtainedbefore decoding the MIB. For example, the UE 170 can first read thesynchronization sequences in the sub-frame 302 to obtain a timing of thesub-frame 302, and subsequently read the MIB of the sub-frame 302.

At step 343, the UE 170 sends a second gap request (also referred to asa measurement request) for a second measurement gap for RSTDmeasurement. Accordingly, assuming PRS positioning occasions of theneighboring cells 141-143 are time aligned and on a same carrierfrequency, the measurement gap 322 can be scheduled that matches thetimings of PRS positioning occasions of the neighboring cells 141-143.At step 344, PRSs from the neighboring cells 141-143 can be received andmeasured. Time differences of arrival of the PRSs can accordingly beobtained. In examples where assistance data includes more than threeneighboring cells, the RSTD measurement may be performed only on aportion of all the listed neighboring cells. For example, the UE 170 maysend a second gap request that includes measurement gaps matching PRSpositioning occasions of a part of all listed neighboring cells.

FIG. 4 shows a flowchart of an exemplary OTDOA positioning process 400according to an embodiment of the disclosure. With reference to FIG. 1,such process 400 can be performed in the wireless communication network100 to locate the UE 170. Messages corresponding to different steps ofthe process 400 are shown transmitted among the UE 170, the gNB basestation 160, the eNodeB base stations 131-133, and the location server110. Particularly, during the process 400, the UE 170 requests ameasurement gap from the serving cell 161 and reads a MIB of theneighboring cell 141 to obtain an SFN of the neighboring cell 141.

At step 410, assistance data and a request for RSTD measurements can betransmitted from the location server 110 to the UE 170 through theserving cell 161. In one example, LPP messages are used for thetransmission of the assistance data. The assistance data can include alist of neighboring cells, for example, the neighboring cells 141-143.One of the neighboring cells 141-143 is used as a reference cell, forexample, the neighboring cell 141. The assistance data can also includeSFN offsets and/or frame timing offsets of the neighboring cells 142-143with respect to the reference cell 141. The assistance data can furtherinclude PRS configurations of each neighboring cell 141-143. Theassistance data can include other information useful for RSTDmeasurement.

At step 412, a first request for a measurement gap to read MIB can betransmitted from the UE 170 to the gNB base station 160, for example, bysending an RRC message. The request may not specify when the measurementgap is supposed to take place because the UE 170 does not have knowledgeof frame timings of the neighboring cells 141-143. However, the requestmay specify the purpose to read a MIB, and include an identity of thereference cell 141. It is noted that obtaining an SFN of any one of theneighboring cells listed in the assistance data is sufficient todetermine SFN timings and PRS positioning occasion timings of eachneighboring cells. Accordingly, the request may include an identity ofany one of the neighboring cells 141-143 other than the reference cell141 in order to carry out RSTD measurement.

At step 414, a first gap pattern can be transmitted from the gNB basestation 160 to the UE 170, for example, by sending an RRC message. Thefirst gap pattern can include configuration information of a measurementgap, such as duration and starting time of the measurement gap. In afirst scenario, the gNB base station 160 can have knowledge of frametimings of the reference cell 141. Accordingly, the gNB base station 160can determine when the measurement gap for reading a MIB is to bescheduled. A measurement gap matching transmission of the MIB can bedetermined. In a second scenario, the gNB base station 160 may not knowframe timings of the reference cell 141. Accordingly, a measurement gapwith a time length larger than a MIB transmission period can beconfigured. The resultant measurement gap provides sufficient time forthe UE 170 to decode a MIB.

At step 416, a MIB of the reference cell 141 can be read by the UE 170during the measurement gap specified in the first gap pattern. The UE170 decodes the MIB to obtain an SFN. At the same time, a frame timingof the reference cell 141 can be obtained according to synchronizationsequences carried in a sub-frame carrying the MIB. Alternatively, frametimings of the reference cell 141 can be obtained by receiving a frametiming offset of the reference cell 141 from the gNB base station 160when the gNB base station 160 knows the frame timings of the referencecell 141. Based on the assistance data and the above obtained frametiming and SFN, the UE 170 can determine timings of PRS positioningoccasions of the neighboring cells 141-143.

At step 418, a second request for measurement gaps for RSTD measurementcan be transmitted from the UE 170 to the gNB base station 160, forexample, by sending an RRC message. The request may include timings ofthe measurement gaps that match PRS positioning occasion timingsobtained at step 416. When PRS positioning occasions of the neighboringcells 141-143 are aligned in time, one measurement gap can be requestedfor the RSTD measurement. Alternatively, when PRS positioning occasionsof the neighboring cells 141-143 occur at different times or theneighboring cells 141-143 operate on different carrier frequencies, morethan one measurement gaps may be requested. In addition, in someexamples, duration of the measurement gaps can be specified according toduration of respective PRS positioning occasions. At step 420, a secondgap pattern can be transmitted from the gNB base station 160 to the UE170 to inform the UE 170 that the requested measurement gaps have beenscheduled. For example, an RRC message can be used for transmission ofthe second gap pattern. The gap pattern can be determined based oninformation carried in the second gap request.

At step 422, PRSs from the multiple neighboring cells 141-143 can bereceived and measured at the UE 170 during the measurement gap (s) ofthe second gap pattern. At step 424, RSTD measurements can be calculatedbased on measured times of arrivals of the PRSs from the neighboringcells 141-143. For example, using the reference cell 141 as a timebasis, time differences of arrival of PRSs between the reference cell141 and other neighboring cells 142-143 can be determined.

At step 426, the RSTD measurements can be transmitted from the UE 170 tothe location server 110, for example, by transmitting an LPP message.The location server 110 can accordingly estimate the position of the UE170 based on the RSTD measurements. In alternative examples, the RSTDmeasurements may not be transmitted to the location server 110. Instead,the UE 170 itself can use the RSTD measurements to determine a locationof the UE 170 with base station location information included in theassistance data.

FIG. 5 shows a flowchart of another exemplary OTDOA positioning process500 according to an embodiment of the disclosure. With reference to FIG.1, such process 500 can be performed in the wireless communicationnetwork 100 to locate the UE 170. Similarly, messages corresponding todifferent steps of the process 500 are shown transmitted among the UE170, the gNB base station 160, the eNodeB base stations 131-133, and thelocation server 110. Different from the process 400, during the process500, the UE 170 can request SFN timing information of a neighboring celllisted in the assistance data from the serving cell 161.

The process 500 includes steps that are similar to that of the process400. For example, steps 510, 518-526 are similar to the steps of 410,418-426. However, steps 512-516 are different from the steps 412-416.Description of steps 510, 518-526 is omitted while steps 512-516 aredescribed below.

At step 512, a request for SFN timing information of a neighboring cell141-143 can be transmitted from the UE 170 to the serving cell 161, forexample, by sending an RRC message. For example, assistance datareceived at step 510 can include a list of neighboring cells, forexample, the neighboring cells 141-143, that are to be measured. Theneighboring cell 141 can be used as a reference cell, and frame timingoffsets and SFN offsets of other neighboring cells 141-143 can bespecified in the assistance data with respect to the reference cell 141.Accordingly, the request can include an identity of the reference cell141.

At step 514, SFN timing information can be transmitted from the servingcell 161 to the UE 170 as a response to the request at step 512. Forexample, the gNB base station 160 can have knowledge of SFN timings ofthe neighboring cells 141-143 due to configuration of the NR network102. In one example, the SFN timing information includes a frame timingoffset and an SFN offset of the reference cell 141 with respect to frametiming and SFN of the serving cell 161. In one example, the SFN timinginformation is carried in an RRC message specific to transmission of theSFN timing information. In another example, a neighboring cell list ason-demand system information can be transmitted to the UE 170. SFNtimings of the neighboring cells 141-143 can be included in entries ofthe neighboring cell list.

In one example, an SFN of the NR network 102 has a length that is longerthan an SFN of the LTE network 101. For example, an NR SFN may have alength of 12 bits while an LTE SFN may have a length of 10 bits.Accordingly, an SFN offset between the LTE SFN and the NR SFN can bedefined modulo 1024 (with respect to a modulus of 1024). For example, anSFN offset between the LTE network 101 and the NR network 102 can becalculated using the following expression,

SFN offset=(LTE SFN−NR SFN)mod 1024,

where LTE SFN and NR SFN correspond to SFNs of an NR LTE frame and anLTE frame under comparison.

At step 516, gap timings needed for RSTD measurement are determined atthe UE 170. For example, based on the assistance data and the receivedSFN timing information of the reference cells 141-143, timings of PRSpositioning occasions of the neighboring cells 141-143 can bedetermined. Accordingly, timings of measurement gaps can be determined.Depending on whether the PRS positioning occasions of the neighboringcells 141-143 are aligned in time, or whether the neighboring cells141-143 operates on different carrier frequencies, one or moremeasurement gaps can be scheduled. A request for a measurement gapincluding timings of at least one gap can subsequently be transmitted.

FIG. 6 shows an exemplary block diagram of a UE 600 according to anembodiment of the disclosure. The UE 600 can be configured to implementvarious embodiments of the disclosure described herein. The UE 600 caninclude a processor 610, a memory 620, and a radio frequency (RF) module630 that are coupled together as shown in FIG. 6. In different examples,the UE 600 can be a mobile phone, a tablet computer, a desktop computer,a vehicle carried device, and the like.

The processor 610 can be configured to perform various functions of theUE 170 described above with reference to FIGS. 1-5. For example, theprocessor 610 can be configured to receive assistance data from alocation server, and accordingly perform RSTD measurement and reportRSTD measurements to the location server. Particularly, the processor610 can be configured to request a measurement gap from a serving cellof the UE 600 and conduct a MIB decoding process to obtain SFN of areference cell included in a list of neighboring cells in the assistancedata. Alternatively, the processor 610 can be configured to request SFNtiming information of the reference cell. Further, the processor 610 canbe configured to subsequently determine PRS positioning occasions of theneighboring cells, and accordingly request a set of measurement gaps toperform the RSTD measurement towards the PRSs from the neighboringcells.

The UE 600 can operate on different types of wireless networks, such asan LTE network, a 5G NR network, and the like. Accordingly, theprocessor 610 can include signal processing circuitry to processreceived or to be transmitted data according to communication protocolscorresponding to different types of wireless networks. Additionally, theprocessor 610 may execute program instructions, for example, stored inthe memory 620, to perform functions related with differentcommunication protocols. The processor 610 can be implemented withsuitable hardware, software, or a combination thereof. For example, theprocessor 610 can be implemented with application specific integratedcircuits (ASIC), field programmable gate arrays (FPGA), and the like,that includes circuitry. The circuitry can be configured to performvarious functions of the processor 610.

In one example, the memory 620 can store program instructions that, whenexecuted by the processor 610, cause the processor 610 to performvarious functions as described herein. For example, the memory 620 canstore program instructions 621 for performing an OTDOA positioningprocess as described in this disclosure. In addition, the memory 620 canstore data related with the OTDOA positioning process, such aspositioning assistance data 622, RSTD measurements 623, and the like.The memory 620 can include a read only memory (ROM), a random accessmemory (RAM), a flash memory, a solid state memory, a hard disk drive,and the like.

The RF module 630 can be configured to receive a digital signal from theprocessor 610 and accordingly transmit a signal to a base station in awireless communication network via an antenna 640. In addition, the RFmodule 630 can be configured to receive a wireless signal from a basestation and accordingly generate a digital signal which is provided tothe processor 610. The RF module 630 can include digital toanalog/analog to digital converters (DAC/ADC), frequency down/upconverters, filters, and amplifiers for reception and transmissionoperations. Particularly, the RF module 630 can include signalprocessing circuits to support the UE 170 to operate on different typesof wireless communication networks, such as a LTE network, a 5G NRnetwork, and the like. For example, the RF module 630 can includeconverter circuits, filter circuits, amplification circuits, and thelike, for processing signals on different carrier frequencies.

The UE 600 can optionally include other components, such as input andoutput devices, additional CPU or signal processing circuitry, and thelike. Accordingly, the UE 600 may be capable of performing otheradditional functions, such as executing application programs, andprocessing alternative communication protocols.

FIG. 7 shows an exemplary block diagram of a base station 700 accordingto an embodiment of the disclosure. The base station 700 can beconfigured to implement various embodiments of the disclosure describedherein. Similarly, the base station 700 can include a processor 710, amemory 720, and a radio frequency (RF) module 730. Those components arecoupled together as shown in FIG. 7. In different examples, the basestation can be an eNodeB in an LTE network, a gNB in an NR network, andthe like.

The processor 710 can be configured to perform various functions of thegNB base station 160 described with reference to FIGS. 1-5. For example,the processor 710 can be configured to schedule a measurement gap for aUE to decode MIB of a reference cell to obtain SFN of the reference cellduring an OTDOA positioning process. When the base station 700 isconfigured with frame timings of the reference cell, the measurement gapcan be configured in a way that the measurement gap matches a MIBtransmission of the reference cell. When the base station 700 does notknow frame timings of the reference cell, a measurement gap having atime length longer than a MIB transmission period of the reference cellcan be configured. Alternatively, the processor 710 can be configured toprovide an SFN offset and frame timing offset to the UE as a response toa request from the UE.

The processor 710 can include signal processing circuits for signalprocessing according to various communication protocols, such asprotocols specified in the 3GPP LTE or 5G NR standards. The processor710 can also be configured to execute program instructions to carry outvarious functions according to the various communication protocols. Theprocessor 710 can be implemented with hardware, software, or acombination thereof. For example, the processor 710 can be implementedwith application specific integrated circuits (ASIC), field programmablegate arrays (FPGA), and the like, that includes circuitry. The circuitrycan be configured to perform various functions of the processor 710.

In one example, the memory 720 can store program instructions that, whenexecuted by the processor 710, cause the processor 710 to performvarious functions described herein. For example, the memory 720 canstore program instructions 721 for scheduling measurement gaps asdescribed in this disclosure. In addition, the memory 720 can store datarelated with an OTDOA positioning process, such as neighboring cellframe timing offsets and/or SFN offsets 722 depending on configurationof the base station 700. Similarly, the memory 720 can include a readonly memory (ROM), a random access memory (RAM), a flash memory, a solidstate memory, a hard disk drive, and the like.

The RF module 730 can have functions and structure similar to that ofthe RF module 630. However, the RF module 730 can have functions andstructures more suitable for performance of the base station 700. Forexample, the RF module 730 can have a higher transmission power forcoverage of a large serving area and multiple UE users, or support moredownlink or uplink component carriers. The RF module 730 can receive ortransmit wireless signals via an antenna 740.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. A single processor or other unit may fulfill the functions ofseveral items recited in the claims. The mere fact that certain measuresare recited in mutually different dependent claims does not indicate,preclude or suggest that a combination of these measures cannot be usedto advantage. A computer program may be stored or distributed on asuitable medium, such as an optical storage medium or a solid-statemedium supplied together with, or as part of, other hardware, but mayalso be distributed in other forms, such as via the Internet or otherwired or wireless telecommunication systems.

While aspects of the present disclosure have been described inconjunction with the specific embodiments thereof that are proposed asexamples, alternatives, modifications, and variations to the examplesmay be made. Accordingly, embodiments as set forth herein are intendedto be illustrative and not limiting. There are changes that may be madewithout departing from the scope of the claims set forth below.

1. A method for observed time difference of arrival (OTDOA) positioning,comprising: receiving, by a user equipment (UE), assistance data from aserving cell of a first network, the assistance data for determining atime difference between the arrival of positioning reference signals(PRSs) received from a plurality of neighboring cells of a secondnetwork; receiving, by the UE, a gap pattern from the serving cell, thegap pattern for decoding a master information block (MIB) of a firstneighboring cell of the plurality of neighboring cells, the gap patternspecifying starting times of multiple measurement gaps during which nouplink or downlink transmissions are scheduled for the UE; anddetermining, by the UE, a system frame number (SFN) timing of the firstneighboring cell based on the gap pattern.
 2. The method of claim 1,wherein the assistance data includes at least one of cell identityinformation of the plurality of neighboring cells, PRS configurationinformation of the plurality of neighboring cells, or SFN timinginformation of the plurality of neighboring cells each indicating anoffset between a neighboring cell and a reference cell that is one ofthe plurality of neighboring cells.
 3. The method of claim 1, furthercomprising: transmitting a decoding request for a measurement gap fordecoding the MIB of the first neighboring cell, the decoding requestincluding an identity of the first neighboring cell without specifying atiming of the measurement gap.
 4. The method of claim 3, wherein themeasurement gaps, whose starting times are specified by the gap pattern,include a measurement gap that matches a MIB transmission of the firstneighboring cell.
 5. The method of claim 3, wherein the measurementgaps, whose starting times are specified by the gap pattern, include ameasurement gap having a length longer than a MIB transmission period ofthe first neighboring cell.
 6. The method of claim 1, furthercomprising: determining timings of PRS positioning occasions of one ormore of the plurality of neighboring cells based on the SFN timing ofthe first neighboring cell and the assistance data; and transmitting ameasurement request for a set of measurement gaps for measuring thePRSs, the measurement request including timings of the set ofmeasurement gaps that match the PRS positioning occasions of the one ormore of the plurality of neighboring cells.
 7. The method of claim 6,further comprising: transmitting measurements of the time difference ofarrival of the PRSs obtained by measuring the PRSs during the set ofmeasurement gaps.
 8. A method for observed time difference of arrival(OTDOA) positioning, comprising: transmitting, by a serving cell of afirst network, assistance data to a user equipment (UE), the assistancedata for determining a time difference between the arrival ofpositioning reference signals (PRSs) received from a plurality ofneighboring cells of a second network at the UE; and transmitting, bythe serving cell, a first gap pattern for decoding a master informationblock (MIB) of a first neighboring cell of the plurality of neighboringcells, the first gap pattern specifying starting times of multiplemeasurement gaps during which no uplink or downlink transmissions arescheduled for the UE.
 9. The method of claim 8, further comprising:receiving by the serving cell a decoding request for a measurement gapfor decoding the MIB of the first neighboring cell, the decoding requestincluding an identity of the first neighboring cell without specifying atiming of the measurement gap.
 10. The method of claim 8, wherein themeasurement gaps, whose starting times are specified by the first gappattern, include a measurement gap that matches a MIB transmission ofthe first neighboring cell.
 11. The method of claim 8, wherein themeasurement gaps, whose starting times are specified by the first gappattern, include a measurement gap having a time length longer than aMIB transmission period of the first neighboring cell.
 12. The method ofclaim 8, further comprising: receiving, by the serving cell, ameasurement request for a set of measurement gaps for measuring thePRSs, the measurement request including timings of the set ofmeasurement gaps that match PRS positioning occasions of one or more ofthe plurality of neighboring cells; transmitting, by the serving cell, asecond gap pattern including the requested set of measurement gaps inresponse to receiving the measurement request for the set of measurementgaps; and receiving, by the serving cell, measurements of the timedifference of arrival of the PRSs from the UE.
 13. (canceled)
 14. A userequipment (UE) comprising: a memory storage comprising instructions; andone or more processor in communication with the memory, wherein the oneor more processors execute the instructions to: receive assistance datafrom a serving cell of a first network, the assistance data fordetermining a time difference between the arrival of positioningreference signals (PRSs) received from a plurality of neighboring cellsof a second network; receive a gap pattern from the serving cell, thegap pattern for decoding a master information block (MIB) of a firstneighboring cell of the plurality of neighboring cells, the gap patternspecifying starting times of multiple measurement gaps during which nouplink or downlink transmissions are scheduled for the UE; and determinea system frame number (SFN) timing timing of the first neighboring cellbased on the gap pattern.
 15. The UE of claim 14, wherein the one ormore processor executes the instructions to: transmit a decoding requestfor a measurement gap for decoding the MIB of the first neighboringcell, the decoding request including an identity of the firstneighboring cell without specifying a timing of the measurement gap. 16.The UE of claim 15, wherein the gap pattern includes a measurement gapthat matches a MIB transmission of the first neighboring cell.
 17. TheUE of claim 15, wherein the measurement gaps, whose starting times arespecified by the gap pattern, include a measurement gap having a timelength longer than a MIB transmission period of the first neighboringcell.
 18. The UE of claim 14, wherein the one or more processor executesthe instructions to: determine timings of PRS positioning occasions ofone or more of the plurality of neighboring cells based on the SFNtiming of the first neighboring cell and the assistance data; andtransmit a measurement request for a set of measurement gaps formeasuring the PRSs, the measurement request including timings of the setof measurement gaps that match the PRS positioning occasions of the oneor more of the plurality of neighboring cells.
 19. The UE of claim 18,wherein the one or more processor executes the instructions to: transmitmeasurements of the time difference of arrival of the PRSs obtained bymeasuring the PRSs during the set of measurement gaps.
 20. The UE ofclaim 14, wherein the first network is a New Radio (NR) network, and thesecond network is a Long Term Evolution (LTE) network.
 21. A servingcell of a first network, the serving cell comprising: a memory storagecomprising instructions; and one or more processor in communication withthe memory, wherein the one or more processors execute the instructionsto: transmit assistance data to a user equipment (UE), the assistancedata for determining a time difference between the arrival ofpositioning reference signals (PRSs) received from a plurality ofneighboring cells of a second network at the UE; and transmit a firstgap pattern for decoding a master information block (MIB) of a firstneighboring cell of the plurality of neighboring cells, the first gappattern specifying starting times of multiple measurement gaps duringwhich no uplink or downlink transmissions are scheduled for the UE.